Conventionally, one example of headrests belonging to the above-noted technical field has been known from a Japanese Laid-Open Patent Publication No. 2006-96125. The headrest described in this literature typically comprises: a main body portion having a top region adapted to be mounted on or above an upper surface of a seat back and a forwardly-overhanging suspended region which extends continuous from a front end of the top region in a downward direction so as to be in a suspended state on a forward side of the headrest; and a headrest stay including a rectilinear portion exposed outwardly from the said top region of the main body portion. This prior art shows a trim cover assembly formed three-dimensionally by sewing in a shape of closed enclosure and describes that a base portion of the headrest stay is embedded in a foam padding filled in the trim cover assembly. Also, shown in the prior art is a headrest stay passage hole formed in the trim cover assembly, and through such headrest stay passage hole, the rectilinear portion of the headrest stay extends and is exposed outwardly. This kind of headrest is the so-called forwardly overhanging type of headrest.